Monitor



FIG. 1 is a front view of the design;

FIG. 2 is a bottom view of the design;

FIG. 3 is a rear view of the design;

FIG. 4 is a top view of the design;

FIG. 5 is a right side view of the design;

FIG. 6 is a left side view of the design; and,

FIG. 7 is a rear view of another embodiment of the design.

The broken lines are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a monitor, as shown and described. 